/*
* Copyright (c) 2006-2007 Erin Catto http://www.gphysics.com
*
* This software is provided 'as-is', without any express or implied
* warranty. In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#ifndef B2_PULLEY_JOINT_H
#define B2_PULLEY_JOINT_H
#include
const float32 b2_minPulleyLength = 2.0f;
/// Pulley joint definition. This requires two ground anchors,
/// two dynamic body anchor points, max lengths for each side,
/// and a pulley ratio.
struct b2PulleyJointDef : public b2JointDef
{
b2PulleyJointDef()
{
type = e_pulleyJoint;
groundAnchorA.Set(-1.0f, 1.0f);
groundAnchorB.Set(1.0f, 1.0f);
localAnchorA.Set(-1.0f, 0.0f);
localAnchorB.Set(1.0f, 0.0f);
lengthA = 0.0f;
maxLengthA = 0.0f;
lengthB = 0.0f;
maxLengthB = 0.0f;
ratio = 1.0f;
collideConnected = true;
}
/// Initialize the bodies, anchors, lengths, max lengths, and ratio using the world anchors.
void Initialize(b2Body* bodyA, b2Body* bodyB,
const b2Vec2& groundAnchorA, const b2Vec2& groundAnchorB,
const b2Vec2& anchorA, const b2Vec2& anchorB,
float32 ratio);
/// The first ground anchor in world coordinates. This point never moves.
b2Vec2 groundAnchorA;
/// The second ground anchor in world coordinates. This point never moves.
b2Vec2 groundAnchorB;
/// The local anchor point relative to bodyA's origin.
b2Vec2 localAnchorA;
/// The local anchor point relative to bodyB's origin.
b2Vec2 localAnchorB;
/// The a reference length for the segment attached to bodyA.
float32 lengthA;
/// The maximum length of the segment attached to bodyA.
float32 maxLengthA;
/// The a reference length for the segment attached to bodyB.
float32 lengthB;
/// The maximum length of the segment attached to bodyB.
float32 maxLengthB;
/// The pulley ratio, used to simulate a block-and-tackle.
float32 ratio;
};
/// The pulley joint is connected to two bodies and two fixed ground points.
/// The pulley supports a ratio such that:
/// length1 + ratio * length2 <= constant
/// Yes, the force transmitted is scaled by the ratio.
/// The pulley also enforces a maximum length limit on both sides. This is
/// useful to prevent one side of the pulley hitting the top.
class b2PulleyJoint : public b2Joint
{
public:
b2Vec2 GetAnchorA() const;
b2Vec2 GetAnchorB() const;
b2Vec2 GetReactionForce(float32 inv_dt) const;
float32 GetReactionTorque(float32 inv_dt) const;
/// Get the first ground anchor.
b2Vec2 GetGroundAnchorA() const;
/// Get the second ground anchor.
b2Vec2 GetGroundAnchorB() const;
/// Get the current length of the segment attached to body1.
float32 GetLength1() const;
/// Get the current length of the segment attached to body2.
float32 GetLength2() const;
/// Get the pulley ratio.
float32 GetRatio() const;
protected:
friend class b2Joint;
b2PulleyJoint(const b2PulleyJointDef* data);
void InitVelocityConstraints(const b2TimeStep& step);
void SolveVelocityConstraints(const b2TimeStep& step);
bool SolvePositionConstraints(float32 baumgarte);
b2Vec2 m_groundAnchor1;
b2Vec2 m_groundAnchor2;
b2Vec2 m_localAnchor1;
b2Vec2 m_localAnchor2;
b2Vec2 m_u1;
b2Vec2 m_u2;
float32 m_constant;
float32 m_ratio;
float32 m_maxLength1;
float32 m_maxLength2;
// Effective masses
float32 m_pulleyMass;
float32 m_limitMass1;
float32 m_limitMass2;
// Impulses for accumulation/warm starting.
float32 m_impulse;
float32 m_limitImpulse1;
float32 m_limitImpulse2;
b2LimitState m_state;
b2LimitState m_limitState1;
b2LimitState m_limitState2;
};
#endif